Virginia is a cash-basis, calendar-year taxpayer. Her salary is $90,000, and she is single. She plans to purchase a residence in 2019. She anticipates her property taxes and interest will total $8,100. Each year, Virginia contributes approximately $4,000 to charity. Her other itemized deductions total approximately $3,500. For purposes of this problem, assume that 2019 tax rates and standard deductions are the same as for 2018.

a. What will her gross tax be in 2018 and 2019 if she contributes $4,000 to charity in each year?

b. What will her gross tax be in 2018 and 2019 if she contributes $8,000 to charity in 2018 but makes no contribution in 2019?

c. What will her gross tax be in 2018 and 2019 if she makes no contribution in 2018 but contributes $8,000 in 2019?
d. Alternative c results in a lower tax than either a or b. Why?